The present invention relates to fluidized bed reactor systems and, more particularly, to fluidized bed reactor systems in which heat energy is introduced into or removed from the fluidized bed in order to provide the heat of reaction for an endothermic reaction or remove the heat of reaction from an exothermic reaction.
Fluidized bed reactors are frequently used for conducting chemical process reactions in which a particulate media is fluidized by a gaseous fluidizing medium. Typically, the fluidized particulate media is one of the reactants and is reacted with a gaseous fluidizing reactant to form the desired gaseous end product which leaves the fluidized bed area as an effluent. Fluidized beds are particularly useful in conducting reactions between two or more gaseous reactants in the presence of a solid catalyst, since the catalyst can be granulated and fluidized by the gaseous reactants. The desired reaction takes place within the fluidized bed area between the gaseous reactants with the gaseous end products then emerging from the fluidized bed for recovery and subsequent utilization. In general, the flow of the fluidized gases, be they reactants, carrier gases, or catalyst, and the size and turbulance of the fluidized particles can be controlled to assure sufficient reactant residence time to allow the reaction to go to completion and form the desired end product.
One problem associated with the use of fluidized bed process reactors is that of accommodating the heat of reaction, that is, adding heat energy to an endothermic reaction and removing excess heat energy from an exothermic reaction. This problem is especially critical when the reaction must occur at a preferred temperature to provide optimum reaction efficiency.
In many fluidized bed systems, coil loops or coil systems are immersed within the fluidized bed and a heat transfer fluid is passed through the coils to either add or remove heat from the bed with the heat energy transferred dependent upon the relative temperature difference between the heat transfer fluid within the coils and the fluidized bed. Since the heat transfer fluid generally travels along an extended path through the coils, the temperature of the fluid can vary greatly as a function of the length of the path travelled and can cause uneven temperature distribution in the fluidized bed. In those cases where it is especially critical that the reaction take place within a relatively narrow, preferred temperature range, these temperature gradients can materially affect the reaction efficiency.